As is well known in the prior art of chair manufacturing, there are various ways to fixedly secure a molded, one piece plastic seat shell to a frame assembly made of steel, wood, plastic or the like. Such prior art chair constructions are exemplified in U.S. Pat. Nos. 3,431,022; 3,459,449; 3,583,759; 3,610,686; and 3,883,176.
In U.S. Pat. No. 3,431,022 to Robert P. Poppe et al. issued on Mar. 4, 1969, there is disclosed a chair construction of the type having a seat portion and a frame including a rail portion disposed adjacent each of a pair of opposite edges of the seat portion. Co-operative means are formed along opposite edges of the seat portion and along the rail portion adjacent each such edge producing a dovetail joint therebetween. The seat portion is assembled to the rail portions by relative sliding of such dovetail joints. In U.S. Pat. No. 3,459,449 to Leo H. Klausen issued on Aug. 5, 1969, there is shown a one-piece molded stacking chair which permits close and efficient stacking of such chairs without the need of reinforcing elements. In U.S. Pat. No. 3,583,759 to Gideon A. Kramer issued on June 8, 1971, there is disclosed an L-shaped, molded plastic shell which is formed of a seat portion and a back portion integrally joined thereto by a flexible concavoconvex waist portion.
U.S. Pat. No. 3,610,686 to Jerome C. Caruso issued on Oct. 5, 1971, teaches a chair which is capable of being stacked for storage and releasably coupled or ganged in side-by-side relation forming a row of like chairs. The chair includes a separate seat assembly and a base assembly. The seat assembly includes a pair of identical, L-shaped frame members between which are mounted a backrest and a seat. The base assembly includes two identical leg units, each having a pair of front or rear legs with shoulder portions to which the ends of a cross member are joined. The leg units are fastened together along inner faces of the cross members so as to form the base assembly. The seat assembly is secured to the base assembly by a mortise and tenon joint. U.S. Pat. No. 3,883,167 to Philip H. Morton issued on May 13, 1975, teaches a one-piece chair shell including a seat portion and a backrest portion connected by a vertically corrugated integral connection section.
However, none of these prior art patents discussed above discloses a high density stacking chair like that of the present invention which allows an interaction between a frame assembly and a separate chair shell. Specifically, when a person seated normally erect in the chair tends to lean back and straighten his legs with respect to his back, the forward edge of the chair shell is deflected forwardly and the upper back portion of the shell is deflected rearwardly so as to "open up" the shell. When the person leans forward back to the neutral or normal erect position, the frame assembly provides a return spring force which forces the chair shell back to its original "at rest" position.